This document discusses CT imaging findings of cerebral ischemia and infarction at different stages. It begins with an overview of the major types of stroke and their causes. It then discusses the pathophysiology of cerebral ischemia and infarction, highlighting the central ischemic focus and less dense ischemic penumbra. Next, it details the imaging appearance of acute, subacute, and chronic infarcts on CT. It notes the hyperdense artery sign seen in some acute infarcts. For subacute infarcts, it describes increased mass effect and hemorrhagic transformation seen 1-7 days later. It also briefly discusses lacunar infarcts and hypoxic-ischemic encephalopathy.

1. CT Imaging of Cerebral Ischemia and Infarction Presented by EKKASIT SRITHAMMASIT, MD. Ann G.Osborn Diagnostic Neuroradiology; 11: 341-369

5. Pathophysiology

6. Physiology of cerebral ischemia and infarction **Most common situation** Densely ischemic central focus Less densely ischemic “penumbra”

7. Physiology of cerebral ischemia and infarction

8. Physiology of cerebral ischemia and infarction **Ischemia produces** Biochemical Reactions Loss of ion homeostasis, Osmotically obligated water, anaerobic glucolysis Loss cell membrane function & Cytoskeletal integrity Cell death

9. Physiology of cerebral ischemia and infarction **Selective vulnerability** Most vulnerable = Neuron Follow by Astrocytes, oligodendroglia, microglia and endothelial cells

10. Physiology of cerebral ischemia and infarction **Collateral supply** Dual or even triple interdigitating supply : Subcortical white matter U-fiber, external capsule, claustrum Short arterioles from a single sourec : The cortex Large, long, single source vessels : Thalamus, basal ganglia, centrum semiovale

12. Border zones / Vascular watershed Adult, term infants Fetus, preterm infant Cortex and cerebellum Deep periventricular region

13. CT Imaging of Cerebral Infarcts

14. CT Imaging of Cerebral Infarcts The imaging manifestations of cerebral ischemia vary significantly with time

15. Acute Infarcts

19. Acute Infarcts Hyperdense MCA

20. Acute Infarcts Obscuration of lentiform nuclei

21. Acute Infarcts Loss of gray-white interfaces ( insular ribbon sign)

22. Acute Infarcts Sulcal effacement

23. Subacute Infarcts

25. Subacute Infarcts

26. Subacute Infarcts

27. Subacute Infarcts

28. Subacute Infarcts ECCT

30. Chronic Infarcts

32. Chronic Infarcts

33. Lacunar Infarcts

35. Lacunar Infarcts

36. Lacunar Infarcts

37. Hypoxic-Ischemic Encephalopathy

40. Border zones / Vascular watershed Adult, term infants Fetus, preterm infant Cortex and cerebellum Deep periventricular region

46. At 2 months of age, T1-weighted brain MR imaging shows high - signal regions in the periventricular area, atrophy of the white matter and serrated ventricular walls .